The present invention generally relates to the continuous casting of metal, especially steel. More precisely, the present invention is concerned with a cooling jacket with which the ingot mold is provided, particularly such ingot molds which contain an electromagnetic inductor for imparting a mixing movement to the cast liquid metal.
A conventional ingot mold for continuous casting of metal may be considered as a continuously cooled mold which is open at its opposite ends and into which the liquid metal is continuously applied at one of the open ends and a partly solidified ingot is likewise continuously extracted from the other open end of the mold.
Such a mold essentially comprises an inner tube, in contact with the liquid metal and determining the cross-section of the ingot to be cast and an outer cooling jacket defining with the inner tube an annular passage for a cooling fluid. The inner tube which is usually formed from copper or copper alloy, assures a good heat transfer between the metal to be cast and the cooling fluid, whereas the cooling jacket is usually made from steel and assures, usually in association with an outer shell, the rigidity and the mechanical resistance of the assembly.
If products of relatively small cross-section, such as billets are to be cast, the mechanical resistance of the inner copper tube, even of small wall thickness, is usually sufficient so that it is not necessary to provide anchoring elements to fix the inner tube to the cooling jacket.
Often such anchoring elements are not provided at all (French Pat. Nos. 2,248,103 and 2,315,344). However, the case is quite different if products of large cross-section, such as blooms or slabs, are to be cast. In such a case the mechanical resistance of the inner copper tube causes a considerable problem since the increase of the width of the walls of the inner tube leads to a reduction of the resistance against bending and to more important heat deformations.
To overcome these shortcomings, which may lead to a discard of the ingot mold after short use, one has already sought to reinforce the inner copper tube by longitudinally extending ribs defining between themselves channels for the cooling fluid (French Pat. Nos. 2,196,866) or to increase their wall thickness up to a value which does not essentially affect the efficiency of the cooling system, and to anchor the inner tube to a casing which itself has a thickness to provide the assembly with the necessary indispensible rigidity. To carry out such construction it is also known to form and tap blind bores in the inner copper tube and to screw into the tapped bores steel pins which traverse openings correspondingly provided in the cooled jacket and provided at their outer ends with nuts abutting against the jacket.
Such ingot molds are, however, not suitable for every kind of application. This is especially the case if the ingot mold is equipped with an electromagnetic inductor to provide a mixing action on the liquid metal passing through the mold and which find an increasing use in the field of the technical endeavor considered. In this kind of ingot mold the tubular inductor surrounds the cooling jacket. In such a construction it is necessary, in order to prevent weakening of the magnetic field during its passing through the cooling jacket and especially the inner copper tube, to place the inductor as closely as possible to the poured metal. For this purpose it is desirable in the first place to reduce as far as possible the thickness of the walls of the cooling jacket and the inner copper tube.
An ingot mold has already been suggested which takes care of the above requirements (French Pat. No. 2,310,821). In this type of ingot mold the cooling jacket is associated with an outer shell, likewise formed from steel, the casing formed by these elements is provided in its interior with support columns formed with axial bores therethrough for the passage of tie rods. These tie rods are screwed at one end thereof into the inner copper tube and at the other end thereof provided with nuts abutting against the outer shell.
Considering the complexity of the mentioned problems, these ingot molds constitute one of the best solutions at present known. Nevertheless, the presence of the columns of the interior of the casing, which contains the inductor, requires a specific construction of the latter and makes the assembly more difficult as far as its construction and the general use of it is concerned (see for instance the French Pat. Nos. 2,324,395 and 2,324,397).